The Overflow Roof Drain (Zurn 100C) is purpose-built to manage heavy stormwater while adding a critical layer of protection against ponding and unexpected blockages. Its dual-discharge design increases hydraulic capacity and provides built-in redundancy. Below, you’ll find a concise overview of how the Zurn 100C Overflow Roof Drain works, where it excels, best-practice installation guidance, and a case study proving its performance.

Overflow Roof Drain – Installation Schematic

What Is an Overflow Roof Drain?

An overflow roof drain provides a secondary path for water so that intense rain or a clogged primary route doesn’t cause roof flooding. The Zurn 100C uses a dual-outlet configuration to split discharge into two independent paths. In practical terms, this means higher flow capacity and added protection if one path is obstructed.

Key Features & Benefits

• Dual-Outlet Overflow Protection: Two discharge paths improve peak flow handling and reduce risk during blockages.
• Rugged Construction: Built for long service life in demanding commercial and industrial environments.
• Dome/Strainer Options: Helps keep debris out while preserving strong intake.
• Flexible Connections: Multiple outlet sizes and connection types for seamless tie-in to your piping layout.
• Risk Reduction: Added redundancy supports code compliance and protects roof assemblies from water damage.

Zurn Brand Reliability

Applications & Use Cases

• Large commercial roofs with high stormwater exposure
• Industrial facilities requiring redundancy for continuity
• Institutional buildings (hospitals, labs, schools) where risk mitigation is critical
• Retrofits seeking overflow protection without major re-piping
• Designs where balanced discharge can optimize downstream pipe sizing

Installation Tips & Best Practices

Proper planning ensures the overflow function works as intended:

• Place the drain at the roof’s low point and confirm slopes direct water to the inlet.
• Select outlet sizes/types to balance both discharge paths under design storm conditions.
• Fit a dome or strainer to minimize debris entry and keep access clear for maintenance.
• Create a watertight tie-in: properly clamp and seal the membrane/flashings.
• Commissioning check: run high-flow tests to verify both outlets perform as expected.

Overflow Roof Drain – Technical Schematic

Case Study: Multi-Tenant Office Complex

Challenge: A large office complex experienced overflow during extreme storms. Single-path drains made the system vulnerable to debris blockages and tenant disruption.

Solution: The design team installed Zurn Overflow Roof Drains at key catchment areas. Each unit split discharge into two separate lines, improving hydraulic performance and redundancy.

Outcome: Across two heavy-rain seasons, there were zero overflow incidents. If one outlet required service, the alternate path maintained drainage. The result: lower maintenance costs and greater reliability.

Conclusion

The Overflow Roof Drain (Zurn 100C) pairs robust construction with dual-outlet protection to keep rooftops safer during peak weather events. When installed to best practice and maintained regularly, it delivers reliable, code-friendly performance for commercial, industrial, and institutional roofs.